Here, two Stanford biologists, Derrick Davis and Tom McFadden bring rap to the horrifically complicated world of gene regulation. Rather than differences in structural genes, it is the regulation of genes that is thought to play a major role in steering a developing embryo into one species or another.

The fact that humans and chimps are so close genetically yet so different phenotypically has led some people into all sorts of confusion about how developmental biology works. I read a book called Why us? by a man called James Le Fanu recently, in which the author seems so overwhelmed by the ability of genetically similar cells to grow into different organisms, that he invokes a "life force" to explain it:

There must be some non-material formative influence that, from the moment of conception, imposes the order of form on the developing embryo of, say, octopus, squid or kangaroo and holds it constant while its cells and tissues are continually renewed as it grow to adulthood.

We cannot, by definition, know that formative "life force" directly, only infer its reality as the missing factor that might bridge the unbridgeable gap between the "first order" reality of the phenomena of life as we know it to be in all its wondrous beauty and diversity and the "second order" reality of its explanation as revealed by those genome projects.

This is a book published this year, in the 21st century, and to me at least, it says something about the pressing need for scientists to make the effort to explain their work, even if it is tricky stuff like gene regulation.